2001a. Two roads to Sparagmos: Extracellular digestion of sedimentary food by bacterial inoculation versus deposit-feeding, p. 335–348

Abstract: Extracellular digestion is a frequent mode of dissolution of dispersed organic detritus in marine sediments. Two geometric modes of deploying this digestive attack are extracorporeal: prokaryotic unicells, and intracorporeal: metazoans with flow-through guts. Enclosed digestive geometry gives metazoans greater ability both to retain digestive agents and to obtain digestive products, allowing them to create digestive conditions more intense than are generally found with communities of sedimentary bacteria. Metazoans hence can dissolve food substrate more quickly. Extracellular hydrolytic enzymes are sorptive for bacteria and dissolved for animals, enhancing both speed and net digestive gain for their respective geometries. Experiments showed little evidence for mass loss of digestive agents to sediments transiting deposit feeders. Standing stocks of sedimentary bacteria-ubiquitously on the order of 10 ° bacteria (cc pore water)- '-set a cap on digestive rates by bacterial inoculations of sediment, and provide metazoans a further kinetic advantage at food concentrations greater than the bacterial biomass. Metazoans therefore have digestive advantage on substrates amenable to concentrated, quick dissolution, suited to their role as high wattage consumers of sedimentary food. Deposit feeding shows strong analogy to laundry technology. The Opportunit